U.S. patent application number 16/534016 was filed with the patent office on 2021-02-11 for active noise reduction in open ear directional acoustic devices.
The applicant listed for this patent is Bose Corporation. Invention is credited to Daniel M. Gauger, JR., Ankita D. Jain, Dale McElhone, Ryan C. Struzik.
Application Number | 20210044882 16/534016 |
Document ID | / |
Family ID | 1000004244350 |
Filed Date | 2021-02-11 |
United States Patent
Application |
20210044882 |
Kind Code |
A1 |
Jain; Ankita D. ; et
al. |
February 11, 2021 |
Active Noise Reduction in Open Ear Directional Acoustic Devices
Abstract
An acoustic device includes at least one acoustic transducer
disposed such that, in a head-worn state, the at least one acoustic
transducer is in an open-ear configuration in which an ear canal of
a user of the acoustic device is unobstructed. The acoustic device
also includes an array of two or more first microphones that
captures audio preferentially from a first direction as compared to
at least a second direction different from the first direction,
wherein the audio captured using the array is processed and played
back through the at least one acoustic transducer, and an active
noise reduction (ANR) engine that includes one or more processing
devices. The ANR engine is configured to generate a driver signal
for the at least one acoustic transducer, the driver signal having
phases that reduce effects of audio captured from at least the
second direction.
Inventors: |
Jain; Ankita D.;
(Westborough, MA) ; Struzik; Ryan C.; (Hopkinton,
MA) ; McElhone; Dale; (Marlborough, MA) ;
Gauger, JR.; Daniel M.; (Berlin, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bose Corporation |
Framingham |
MA |
US |
|
|
Family ID: |
1000004244350 |
Appl. No.: |
16/534016 |
Filed: |
August 7, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04R 2460/01 20130101;
H04R 1/105 20130101 |
International
Class: |
H04R 1/10 20060101
H04R001/10 |
Claims
1. An acoustic device comprising: at least one acoustic transducer
disposed such that, in a head-worn state, the at least one acoustic
transducer is in an open-ear configuration in which an ear canal of
a user of the acoustic device is unobstructed; an array of two or
more first microphones that captures audio preferentially from a
first direction as compared to at least a second direction
different from the first direction, wherein the audio captured
using the array is processed and played back through the at least
one acoustic transducer; and an active noise reduction (ANR) engine
comprising one or more processing devices, the ANR engine
configured to generate a driver signal for the at least one
acoustic transducer, the driver signal having phases that reduce
effects of audio captured from at least the second direction.
2. The acoustic device of claim 1, wherein the ANR engine is
configured to reduce the effects of the audio captured from the
second direction in a 300-1500 Hz frequency band.
3. The acoustic device of claim 2, wherein the ANR engine is
configured to increase a power ratio of (i) audio signals in the
300-1500 Hz frequency band, as captured from the first direction
and (ii) audio signals in the 300-1500 Hz frequency band, as
captured from at least the second direction, by at least 5 dB.
4. The acoustic device of claim 1 further comprising at least a
second microphone to capture audio from the second direction.
5. The acoustic device of claim 4, wherein in the head-worn state,
the second microphone is located behind a pinna of the user.
6. The acoustic device of claim 1, further comprising an amplifier
circuit configured to process the audio captured using the
array.
7. The acoustic device of claim 1, wherein the at least one
acoustic transducer and the array of two or more first microphones
are disposed along a temple of an eye-glass frame.
8. The acoustic device of claim 1, wherein the first direction is
an estimated direction of gaze of the user of the acoustic
device.
9. The acoustic device of claim 1, wherein the audio captured using
the array is processed using a beamforming process to capture audio
from the first direction.
10. The acoustic device of claim 1, wherein the at least one
acoustic transducer and the array of two or more first microphones
are disposed in an open-ear headphone.
11. The acoustic device of claim 1, wherein the at least one
acoustic transducer is a part of an array of acoustic
transducers.
12. The acoustic device of claim 1, wherein in the head-worn state,
a magnitude and phase of a sound pressure response from the at
least one acoustic transducer to a microphone is substantially
similar to a sound pressure response from the at least one acoustic
transducer to a location of an ear canal.
13. The acoustic device of claim 1, wherein in the head-worn state,
a mainlobe of a radiation pattern of the at least one acoustic
transducer is directed towards the ear canal of the user, and a
power ratio of (i) a portion of output of the at least one acoustic
transducer radiated towards the ear canal of the user and (ii) a
portion of output of the at least one acoustic transducer radiated
towards a microphone of the array is at least 10 dB.
14. The acoustic device of claim 1, wherein the ANR engine
comprises an analog to digital converter, an amplifier,
compensator, and a digital to analog converter.
15. A set of wearable audio eyeglasses comprising: a frame
comprising: a frontal region that includes a pair of lens
receptacles, and a bridge disposed between the lens receptacles, a
pair of arms extending from the frontal region of the frame; at
least one acoustic transducer disposed in one of the pair of arms,
the acoustic transducer configured to direct audio output towards
an ear of a user in a head-worn state of the audio eyeglasses; an
array of two or more first microphones that captures audio
preferentially from a first direction as compared to at least a
second direction different from the first direction; and an
electronics module comprising: an amplifier circuit that receives
the audio captured using the array, and generates a first driver
signal for the at least one acoustic transducer based on the audio,
and an active noise reduction (ANR) engine comprising one or more
processing devices, wherein the ANR engine generates a second
driver signal for the at least one acoustic transducer, the second
driver signal having phases that reduce effects of audio captured
from at least the second direction.
16. The wearable audio eyeglasses of claim 15, wherein the ANR
engine reduces the effects of the audio captured from the second
direction in a 300-1500 Hz frequency band.
17. The wearable audio eyeglasses of claim 16, wherein the ANR
engine is configured to increase a power ratio of (i) audio signals
in the 300-1500 Hz frequency band, as captured from the first
direction and (ii) audio signals in the 300-1500 Hz frequency band,
as captured from at least the second direction, by at least 5
dB.
18. The wearable audio eyeglasses of claim 15 further comprising at
least a second microphone to capture audio from the second
direction.
19. The wearable audio eyeglasses of claim 18, wherein in the
head-worn state, the second microphone is located behind a pinna of
the user.
20. The wearable audio eyeglasses of claim 15, wherein in the
head-worn state, a mainlobe of a radiation pattern of the at least
one acoustic transducer is directed towards the ear canal of the
user, and a power ratio of (i) a portion of output of the at least
one acoustic transducer radiated towards the ear canal of the user
and (ii) a portion of output of the at least one acoustic
transducer radiated towards a microphone of the array is at least
10 dB.
Description
TECHNICAL FIELD
[0001] This disclosure generally relates to wearable open-ear
acoustic devices.
BACKGROUND
[0002] Wearable audio devices, such as off-ear headphones, produce
sound using an electro-acoustic transducer that is spaced from the
user's ear canal entrance. These wearable audio devices may take
various form factors. In some cases, these wearable audio devices
include audio eyeglasses configured to rest on the ears and nose of
the user. The audio eyeglasses can include transducers proximate
one or both of the user's ears, e.g., located on the arms of the
eyeglasses.
SUMMARY
[0003] In one aspect, this document features an acoustic device
that includes at least one acoustic transducer disposed such that,
in a head-worn state, the at least one acoustic transducer is in an
open-ear configuration in which an ear canal of a user of the
acoustic device is unobstructed. The acoustic device also includes
an array of two or more first microphones that captures audio
preferentially from a first direction as compared to at least a
second direction different from the first direction, wherein the
audio captured using the array is processed and played back through
the at least one acoustic transducer, and an active noise reduction
(ANR) engine that includes one or more processing devices. The ANR
engine is configured to generate a driver signal for the at least
one acoustic transducer, the driver signal having phases that
reduce effects of audio captured from at least the second
direction.
[0004] In another aspect, this document features a set of wearable
audio eyeglasses that includes a frame, at least one acoustic
transducer, an array of two or more first microphones, and an
electronics module. The frame includes a frontal region that
includes a pair of lens receptacles, and a bridge disposed between
the lens receptacles. The frame also includes a pair of arms
extending from the frontal region of the frame. The at least one
acoustic transducer is configured to direct audio output towards an
ear of a user in a head-worn state of the audio eyeglasses. The
array of two or more first microphones captures audio
preferentially from a first direction as compared to at least a
second direction different from the first direction. The
electronics module includes an amplifier circuit that receives the
audio captured using the array, and generates a first driver signal
for the at least one acoustic transducer based on the audio. The
electronics module also includes an active noise reduction (ANR)
engine comprising one or more processing devices, wherein the ANR
engine generates a second driver signal for the at least one
acoustic transducer, the second driver signal having phases that
reduce effects of audio captured from at least the second
direction.
[0005] Implementations of the above aspects can include one or more
of the following features. The ANR engine can be configured to
reduce the effects of the audio captured from the second direction
in a 300-1500 Hz frequency band. The ANR engine can be configured
to increase a power ratio of (i) audio signals in the 300-1500 Hz
frequency band, as captured from the first direction and (ii) audio
signals in the 300-1500 Hz frequency band, as captured from at
least the second direction, by at least 5 dB. The acoustic device
can include at least a second microphone to capture audio from the
second direction. In the head-worn state, the second microphone can
be located behind a pinna of the user. The acoustic device can
include an amplifier circuit configured to process the audio
captured using the array. The at least one acoustic transducer and
the array of two or more first microphones can be disposed along a
temple of an eye-glass frame. The first direction can be an
estimated direction of gaze of the user of the acoustic device. The
audio captured using the array can be processed using a beamforming
process to capture audio from the first direction. The at least one
acoustic transducer and the array of two or more first microphones
can be disposed in an open-ear headphone. The at least one acoustic
transducer can be a part of an array of acoustic transducers. In
the head-worn state, the magnitude and phase of a sound pressure
response from the at least one acoustic transducer to a microphone
can be substantially similar to a sound pressure response from the
at least one acoustic transducer to a location of an ear canal. In
the head-worn state, a mainlobe of a radiation pattern of the at
least one acoustic transducer can be directed towards the ear canal
of the user, and a power ratio of (i) a portion of output of the at
least one acoustic transducer radiated towards the ear canal of the
user and (ii) a portion of output of the at least one acoustic
transducer radiated towards a microphone of the array can be at
least 10 dB. The ANR engine can include an analog to digital
converter, an amplifier, compensator, and a digital to analog
converter.
[0006] Various implementations described herein may provide one or
more of the following advantages. An array of microphones disposed
in an open-ear device can facilitate directional capture, for
example, to amplify audio coming from a particular direction (e.g.,
look/gaze direction of the user). One or more acoustic transducers
can facilitate delivery of audio to user's ears without significant
coupling to the microphones. In some cases, one or more of the
microphones can be disposed at locations substantially close to the
ears such that signals detected by such microphone(s) can be used
as a reference for an echo canceler. Use of such echo cancelers can
potentially improve the quality of audio delivered to the user's
ears thereby improving the user experience.
[0007] In some cases, the open-ear devices can also include a
feedforward and/or feedback active noise reduction (ANR) signal
paths that can be configured to improve a signal to noise ratio
(SNR) from a particular direction (e.g., look/gaze direction of the
user) by at least 5 dB. Such improvement over a particular portion
of the spectrum (e.g., a portion of the speech band) can
potentially improve speech intelligibility for some users. The
noise reduction (possibly in combination with the directional
capture/amplification) in turn can improve the feasibility of using
open-ear devices not only as hearing aids, but also generally as
hearing assistance devices that improve speech intelligibility for
users who do not have hearing loss.
[0008] In general, the technology described herein can potentially
improve the acoustic performances of open-ear audio devices such as
audio eyeglasses or head-mounted acoustic devices. In some cases,
the improvements in directional capture, SNR, and/or reduction in
coupling between microphones and acoustic transducers can
facilitate the use of open ear devices such as hearing aids. Such
open-ear form factors can make hearing aids more acceptable (e.g.,
from a social use standpoint) to some users, particularly ones who
are hesitant to use them otherwise.
[0009] Two or more of the features described in this disclosure,
including those described in this summary section, may be combined
to form implementations not specifically described herein. The
details of one or more implementations are set forth in the
accompanying drawings and the description below. Other features,
objects, and advantages will be apparent from the description and
drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A shows a schematic depiction of a pair of audio
eyeglasses as an example of an open-ear acoustic device.
[0011] FIG. 1B is a schematic depiction of an electronics module
included in the audio eyeglasses of FIG. 1A.
[0012] FIG. 2 is a block diagram of multiple signal paths in an ANR
device.
[0013] FIG. 3 is a heat map diagram illustrating an acoustic
distribution over a surface of an arm of a pair of audio eyeglasses
depicted in FIG. 1A.
DETAILED DESCRIPTION
[0014] This document describes technology for facilitating capture
of audio signals in open-ear acoustic devices, and delivering the
captured (and amplified) audio to user's ears such that the
coupling between microphones and acoustic transducers is not
significant, and the output of the acoustic transducers is low
enough to not reach other people in the vicinity of the user. In
addition, this document also describes feedforward and feedback
noise reduction processes that allow for reducing the effect of
audio coming from directions outside of one or more target
directions. Such noise reduction, particularly in portions of the
speech band, can result in at least 5 dB of improvement in signal
to noise ratio (SNR), which in turn can improve speech
perception/intelligibility even for users who do not have hearing
loss. When combined with the directional capture of audio using
microphone arrays, the technology described herein can allow a user
to select the target direction from which audio is to be
emphasized. For example, the target direction can be the direction
at which a user is looking--referred to herein as the look
direction or gaze direction of the user.
[0015] FIG. 1A shows a schematic depiction of a pair or set of
wearable audio eyeglasses 10 as an example of an open-ear acoustic
device. As shown, the audio eyeglasses 10 can include a frame 20
having a frontal region 30 and a pair of arms (also referred to as
temples) 40a and 40b (40, in general) extending from the frontal
region 30. As with conventional eyeglasses, the frontal region 30
and arms 40 are designed for resting on the head of a user. The
frontal region 30 can include a set of lenses 50 fitted to
corresponding lens receptacles. The two lens receptacles are
connected by a bridge 60 (which may include padding) for resting on
the user's nose in a head-worn state of the audio eyeglasses. The
lenses can include prescription, non-prescription and/or
light-filtering lenses. Arms 40 can include a contour 65 for
resting on the user's respective ears.
[0016] The frame 20 includes electronics module 70 and other
components for controlling the audio eyeglasses 10 according to
particular implementations. In some cases, separate, or duplicate
sets of electronics module 70 are included in portions of the
frame, e.g., each of the respective arms 40 in the frame 20.
However, certain components described herein can also be present in
singular form. Also, while the electronics module 70 is disposed in
the arms 40 of the frame 20, in some implementations, at least
portions of the electronics module 70 may be disposed elsewhere in
the frame (e.g., in a portion of the frontal region 30 such as the
bridge 60).
[0017] FIG. 1B is a schematic depiction of the electronics module
70 included in the audio eyeglasses of FIG. 1A. In some
implementations, the components in electronics module 70 may be
implemented as hardware and/or software, and such components may be
connected to one another by hard-wired and/or wireless connections.
In some implementations, the components described as connected or
coupled to other components in audio eyeglasses 10 or other
systems, may communicate over hard-wired connections and/or using
communications protocols. In some implementations, the electronics
module 70 includes a transceiver 72 and an antenna 74 that
facilitates wireless communication with another electronics module
and/or other wireless-enabled devices such as a mobile phone,
tablet, or smartwatch. In some cases, the communications
protocol(s) used by the electronics module 70 in communicating with
one another can include, for example, a Wi-Fi protocol using a
wireless local area network (LAN), a communication protocol such as
IEEE 802.11 b/g, a cellular network-based protocol (e.g., third,
fourth or fifth generation (3G, 4G, 5G cellular networks) or one of
a plurality of internet-of-things (IoT) protocols, such as:
Bluetooth, BLE Bluetooth, ZigBee (mesh LAN), Z-wave (sub-GHz mesh
network), 6LoWPAN (a lightweight IP protocol), LTE protocols, RFID,
ultrasonic audio protocols, etc.
[0018] In some implementations, the electronics module 70 includes
one or more electroacoustic transducers 80 disposed such that, in a
head-worn state of the corresponding device, the one or more
electroacoustic transducers 80 are in an open-ear configuration.
This refers to a configuration in which there exists a physical
separation between an ear canal of a user and the corresponding
acoustic transducer such that the acoustic transducer (and/or other
portions of the corresponding device) does not fully occlude the
ear canal from the environment. For example, referring back to FIG.
1, an acoustic transducer 80 can be disposed on an arm 40 of the
audio eyeglasses 10, such that the transducer 80 does not cover the
ear canal of the user. In some implementations, at least two
electroacoustic transducers 80 are positioned proximate to (but
physically separated from) the ears of the user (e.g., one
transducer 80 proximate to each ear. In some implementations, the
one or more transducers 80 can be disposed to extend from the arms
40 such that they (or their respective housings or structures for
interfacing with the ear) physically contact at least a portion of
the ears of the user while not occluding the ear canals from the
environment. It is noted, however, that while the audio eyeglasses
10 of FIG. 1A are shown as an example of a head-worn open-ear
acoustic device, other types of open-ear devices are also within
the scope of this disclosure. For example, the technology described
herein can be used in open-ear headphones or other head-worn
acoustic devices, examples of which are shown in U.S. Pat. Nos.
9,794,676, and 9,794,677, the contents of which are incorporated
herein by reference.
[0019] In some implementations, each transducer 80 can be used as a
dipole loudspeaker with an acoustic driver or radiator that emits
front-side acoustic radiation from its front side, and emits
rear-side acoustic radiation from its rear side. The dipole
loudspeaker can be built into the frame 20 of the audio eyeglasses
10. In some implementations, an acoustic channel defined within the
housing of the eyeglasses 10 (e.g. within the arms 40) can direct
the front-side acoustic radiation and another acoustic channel can
direct the rear-side acoustic radiation. A plurality of
sound-conducting vents (openings) in the housing allow sound to
leave the housing. Openings in the eyeglass frame 20 can be aligned
with these vents, so that the sound also leaves the frame 20. In
some implementations, the distance between the sound-conducting
openings defines an effective length of an acoustic dipole of the
loudspeaker. The effective length may be considered to be the
distance between the two openings that contribute most to the
emitted radiation at any particular frequency. The housing and its
openings can be constructed and arranged such that the effective
dipole length is frequency dependent. In certain cases, the
transducer 80 (e.g., loudspeaker dipole transducer) is able to
achieve a higher ratio of (i) sound pressure delivered to the ear
to (ii) spilled sound, as compared to an off-ear headphone not
having this feature. Exemplary dipole transducers are shown and
described in U.S. patent application Ser. No. 16/151,541, filed
Oct. 4, 2018; and Ser. No. 16/408,179, filed May 9, 2019.
[0020] The electronics module 70 can also include an array 75 of
one or more microphones. In some implementations, the microphones
in the array 75 can be used to capture audio preferentially from a
particular direction. For example, each of the microphones in the
array 75 can be inherently directional that capture audio from a
particular direction. In other examples, the audio captured by the
array can be processed (e.g., using a smart antenna or beamforming
process) to emphasize the audio captured from a particular
direction. In some implementations, the microphone array 75
captures ambient audio preferentially from a first direction (e.g.,
as compared to at least a second direction that is different from
the first direction). For example, the microphone array 75 can be
configured to capture/emphasize audio preferentially from the front
of the frame 20 along a direction parallel to the two arms 40. In
some cases, this allows for preferential capture of audio from a
direction that coincides with the gaze direction of the user of the
audio eyeglasses 10. In implementations where the captured audio is
played back through the one or more acoustic transducers 80
(possibly with some amplification), this can allow for a user to
change a direction of gaze to better hear the sounds coming from
that direction, as compared to, for example, sounds coming from
other directions. In some implementations, to facilitate such
amplification, the electronic module 70 includes an amplifier
circuit 86 that processes signals representing the audio captured
using the microphones of the array 75, and generates driver signals
for the one or more acoustic transducers 80. In some cases, this
can be improve the user's perception of speech in noise
environments. For example, even a 5-10 dB improvement in the ratio
of power from a particular direction to the power from other
directions can improve perception of speech, particularly when the
improvement is within the speech band (e.g., in the 300-1500 Hz
frequency band) of the audio spectrum.
[0021] The multiple microphones can be disposed in the
corresponding device in various ways. For the example device (audio
eyeglasses 10) of FIG. 1A, the one or more microphones of the array
75 may be disposed along an arm or temple 40 of the eyeglass frame
20. In some implementations, at least one microphone of the array
75 may be disposed in the frontal region 30 (e.g., on the bridge
60) of the frame 20. In some implementations, the microphones of
the array 75 can be separate from any microphones that are disposed
for the purpose of capturing the voice of the user (e.g., for
spoken commands, phone conversations etc.). In some
implementations, one or more microphones of the array 75 can also
be used for capturing the voice of the user.
[0022] In some implementations, the locations of the microphones in
the array 75 and the locations of the one or more acoustic
transducers 80 can be jointly determined to implement an acoustics
package that provides for directional audio delivery and capture in
open-ear acoustic devices. For example, the locations of the
transducers 80 and the microphones in the array 75 can be
determined such that the transducers 80 satisfactorily deliver
audio towards the ear of the user, without directing audio towards
a microphone over a target or threshold amount. For example, the
one or more acoustic transducers 80 and the multiple microphones of
the array 75 can be disposed on a head-worn acoustic device (e.g.,
the audio eyeglasses 10) such that, in the head-worn state, a
mainlobe of a radiation pattern of a directional acoustic
transducer is directed towards the ear canal of the user, while a
power ratio of (i) a portion of output of the one or more acoustic
transducers radiated towards the ear canal of the user and (ii) a
portion of output of the at least one acoustic transducer radiated
towards a microphone of the array 75 satisfies a threshold
condition. For example, a threshold condition can dictate that the
above-referenced power ratio is at least 10 dB. In some
implementations, the locations of the transducers 80 and the
microphones of the array 75 can be determined while accounting for
the directionality of the transducers, and/or the microphones,
and/or the corresponding arrays.
[0023] In some implementations, the locations of the microphones of
the array 75 are determined first, and the locations of the
acoustic transducers 80 are then determined to achieve the target
performances discussed above. For example, once the locations
associated with the microphone array 75 are determined, the
locations of the one or more acoustic transducers 80 are then
determined such that the transducers 80 satisfactorily deliver
audio towards the ear of the user, without directing audio towards
a microphone of the array 75 over the target or threshold amount.
Where a dipole transducer is used, the microphone(s) may be located
in or near an acoustic null in a radiation pattern of the dipole
transducer. In some cases, the microphone is positioned in a region
in which acoustic energy radiated from a first radiating surface of
the transducer destructively interferes with acoustic energy
radiated from a second radiating surface of the transducer.
[0024] In some implementations, the electronics module 70 includes
a controller 82 that coordinates and controls various portions of
the electronic module 70. The controller 82 can include one or more
processing devices that, in communication with one or more
non-transitory machine-readable storage devices, execute various
operations of the electronic module 70. In some implementations,
the controller 82 implements an active noise reduction (ANR) engine
84 that generates driver signals for reducing the effect of audio
signals that are considered as "noise." For example, in a
particular use-case scenario, the audio captured from a particular
direction (e.g., the gaze direction of a user) can be considered to
be a signal of interest, and the audio captured from other
directions can be considered to be noise. The ANR engine 84 can be
configured to generate one or more driver signals that have phases
that are substantially inverted with respect to the phases of the
noise signal, such that the driver signals generated by the ANR
engine 84 destructively interferes with the noise signal (based on
the principles of superposition) to reduce the effects of the
noise.
[0025] In some implementations, the ANR engine 84 can include
multiple noise reduction pathways such as a feedback path and a
feedforward path (generally referred to as ANR pathways, ANR signal
paths) that require the use of microphones to capture corresponding
reference signals. In some implementations, one or more microphones
of the array 75 can be used as a microphone for an ANR signal path,
and in such cases, the placement of the corresponding microphones
can be governed by whether the microphones are used for capturing
reference audio for feedforward path or a feedback path. However,
to facilitate an understanding of such placements, a description of
an ANR engine 84 is provided first.
[0026] Various signal flow topologies can be implemented in the ANR
engine to enable functionalities such as echo cancellation,
feedback noise cancellation, feedforward noise cancellation, etc.
For example, as shown in the example block diagram of an ANR engine
84 in FIG. 2, the signal flow topologies can include a feedforward
noise reduction path 210 that drives the output transducer 80 to
generate an anti-noise signal (using, for example, a feedforward
compensator 212) to reduce the effects of a noise signal picked up
by the feedforward microphone 202. In another example, the signal
flow topologies can include a feedback noise reduction path 214
that drives the output transducer 80 to generate an anti-noise
signal (using, for example, a feedback compensator 216) to reduce
the effects of a noise signal picked up by the feedback microphone
204. The signal flow topologies can also include an additional
signal processing path 218 that includes circuitry (e.g., an echo
canceller 220) for further improving the noise reduction
performance of the ANR engine 84. In some implementations, the ANR
engine 84 can include a configurable digital signal processor
(DSP), which can be used for implementing the various signal flow
topologies and filter configurations. Examples of such DSPs are
described in U.S. Pat. Nos. 8,073,150 and 8,073,151, which are
incorporated herein by reference in their entirety. The ANR engine
84 can also include one or more additional components such as an
analog to digital converter (to convert the analog signal captured
by a microphone to a digital signal that can be processed by a
processing device), and a digital to analog converter (to convert
the output of a processing device to a signal that is reproducible
by a transducer 80).
[0027] In some implementations, the feedforward microphone 202
and/or the feedback microphone 204 can be included in the
microphone array 75. In such cases, the locations for the
feedforward microphone 202 and/or the feedback microphone 204 may
be determined first, before determining the locations for the one
or more transducers 80. For example, the feedback microphone 204
can be disposed on the device at a location such that in a
head-worn state of the device, the feedback microphone 204 is
located close to the ear of the user. This can result in a high
degree of coherence between what the user actually hears and what
the microphone captures. Referring back to FIG. 1A, the location 42
represents a possible location for the feedback microphone 204. An
acoustic transducer 80 (e.g., a dipole) can then be placed such
that the feedback microphone is located in the null of the dipole.
This can be particularly advantageous in some applications, for
example, when the audio eyeglasses 10 are being used as hearing
aids. In some implementations, the feedback microphone may be at a
location where the transfer function of an acoustic path between
the transducer 80 and the microphone is similar in magnitude and
phase to the transfer function of an acoustic path between the
transducer and the ear canal. As such, configuring the ANR engine
to control sound at the feedback microphone will yield similarly
controlled sound at the ear canal, since this microphone location
serves as an approximate proxy for the ear canal for sound from
both the transducer and the environment. For a pair of audio
eyeglasses 10, a feedforward microphone 202 can be placed, for
example, at a location such that the microphone is located behind
the pinna of a user in a head-worn state of the device. Referring
back to FIG. 1A, the location 44 at the end of an arm 40 represents
a possible location for a feedforward microphone. In some
implementation, such behind-the-pinna location of the feedforward
microphone 202 allows for effective feedforward cancellation of
sounds coming from behind the user in a head-word state of the
device, which in turn improves the perception of sounds coming from
the frontal direction (e.g., that may coincide with the gaze
direction of the user).
[0028] In some implementations, the performance of an open ear
device can be further improved by implementing an echo canceler (or
echo cancellation circuit) that reduces the effects of any output
of the transducer 80 as picked by a microphone such as the feedback
microphone 204. For example, a reference microphone 208 can be used
for picking up a different version of a signal that is also picked
up or captured by the feedback microphone 204. Based on the two
versions of the signal, an echo cancellation circuit (Kecho) 220
can generate an additional signal, which, when combined with the
output of the feedback compensator 216, further reduces the effect
of coupling between the transducer 80 and the microphones. While
the echo cancellation circuit shown in the example of FIG. 2 is for
canceling echoes pertaining to the feedback signal path, a similar
echo canceler can be implemented for the feedback signal path with
or without the echo canceler in the feedback path. In some
implementations, the echo cancellation circuit includes a biquad
filter that generates a reference signal for the echo cancellation
(or feedback cancellation in case of hearing aids).
[0029] Referring back to FIG. 1B, the electronics module 70 can
also include an inertial measurement unit (IMU) 90, and a power
source 100. In various implementations, the power source 100 is
connected to the transducer 80, and can additionally be connected
to the IMU 90. Each of the transducer 80, IMU 90 and power source
100 are connected with the controller 82, which is configured to
perform control functions according to various implementations
described herein. The IMU 90 can include a microelectromechanical
system (MEMS) device that combines a multi-axis accelerometer,
gyroscope, and/or magnetometer. It is understood that additional or
alternative sensors may perform functions of the IMU 90, e.g., an
optical-based tracking system, accelerometer, magnetometer,
gyroscope or radar for detecting movement as described herein. The
IMU 90 can be configured to detect changes in the physical location
and/or orientation of the audio eyeglasses 10 to enable
location/orientation-based control functions. The electronics
module 70 could also include one or more optical or visual
detection systems located at the audio eyeglasses 10 or another
connected device configured to detect the location/orientation of
the audio eyeglasses 10. In any case, the IMU 90 (and/or additional
sensors) can provide sensor data to the controller 82 about the
location and/or orientation of the audio eyeglasses 10.
[0030] The power source 100 to the transducer 80 can be provided
locally (e.g., with a battery in each of the temple regions of the
frame 20), or a single battery can transfer power via wiring that
passes through the frame 20 or is otherwise transferred from one
temple to the other. The power source 100 can be used to control
operation of the transducer 80, according to various
implementations.
[0031] The controller 82 can include conventional hardware and/or
software components for executing program instructions or code
according to processes described herein. For example, controller 82
may include one or more processing devices, memory, communications
pathways between components, and/or one or more logic engines for
executing program code. Controller 82 can be coupled with other
components in the electronics module 70 via any conventional
wireless and/or hardwired connection which allows controller 82 to
send/receive signals to/from those components and control operation
thereof.
[0032] Referring back to FIG. 1A (and with continued reference to
FIG. 1B), in certain implementations, the audio eyeglasses 10
include an interface 95, which is connected with the controller 82.
In these cases, the interface 95 can be used for functions such as
audio selection, powering on the audio eyeglasses or engaging a
voice control function. In certain cases, the interface 95 includes
a button or a capacitive touch interface. In some additional
implementations, the interface 95 includes a compressible
interface, which can allow a user to squeeze one or more sections
of the audio eyeglasses 10 (e.g., arms 40) to initiate a user
interface command. In some implementations, the interface 95 can
include one or more microphones that are used for capturing spoken
commands from the user. In some implementations, one or more
microphones pertaining to the interface 95 can also be a part of
the microphone array 75. In some implementations, the microphones
of the interface 95 can be directional, or be a part of a
directional array that captures sound preferentially from the
direction of the user's mouth.
[0033] FIG. 3 is a heat map diagram 300 illustrating an acoustic
distribution over a surface of an arm 40 of a pair of audio
eyeglasses depicted in FIG. 1A. Such an acoustic distribution
diagram 300 represents the radiation pattern of the underlying one
or more acoustic transducers, and can be used for placements of the
one or more microphones in accordance with the technology herein.
The heat map diagram can vary as a function of frequency, and
diagrams for multiple frequencies or frequency ranges may need to
be considered for determining optimal locations for acoustic
transducers and/or microphones. The example of FIG. 3 illustrates
the heat map diagram for 1000 Hz audio emanating from a dipole
acoustic transducer (also referred to as an acoustic dipole) having
two ends at the locations 405a and 405b, respectively. The heat map
illustrates a distribution of surface pressure at various locations
normalized with respect to a surface pressure at the ear.
Therefore, the heat map tracks the variation in the ratio of two
quantities--(i) G.sub.od--amount of coupling between an acoustic
transducer and a microphone placed at the corresponding location,
and (ii) G.sub.ed--amount of coupling between the acoustic
transducer and a location of the ear--as a function of locations on
the arm 40. The one or more microphones can be placed at locations
where the ratio is low (or more negative when expressed in dB).
Therefore, the shades that are towards the bottom 315 of the heat
map legend represent good locations for placement of microphones,
and shades that are towards the top 310 of the heat map legend
represent locations where a microphone is likely to pick up audio
that approximates what is heard at the location of the ear. In the
example of FIG. 3, the area 320 represents locations where the
ratio is very low (e.g., as expected at acoustic nulls in a
radiation pattern of an acoustic transducer such as a dipole),
making such locations suitable for placement of one or more
microphones. Similarly, the ratio is very low at the location 325
(at the back end of the arm 40) making the location ideal for
placement of one or more feedforward microphones 202 as described
above with reference to FIG. 2. In some implementations, one or
more feedback microphones 204 may be placed near the ear canal, in
order to be coherent with the environmental sound signal at the ear
canal. This can be done, for example, by placing the one or more
feedback microphones along the heat map contours where the mapped
ratio is approximately 0 dB, e.g., at the boundary between the
lightest gray and white contours. In such cases the audio received
from the transducer 80, as picked up by a feedback microphone,
approximates the audio reaching the ear canal from the transducer
80.
[0034] While a distinction has sometimes been made between feedback
and feedforward microphones, in acoustic devices such as open ear
acoustic devices, a feedforward microphone could capture some
amount of the transducer signal and thus have potential for
feedback behavior. Therefore, the one or more microphones and their
respective locations can be thought of more generally as being more
or less able to capture either environmental sound signals or
transducer sound signals coherent with the ear canal. Microphone
locations corresponding to ratios close to unity (or approximately
0 dB) in the heat map may be better suited for accurately capturing
the environmental sound signal at the ear canal at the expense of
stability of the ANR system and vice-versa. Nonetheless, for a
specific transducer and microphone system configuration, the ANR
engine can be designed to account for those tradeoffs generally
without making a rigid distinction between feedback and feedforward
paths.
[0035] The functionality described herein, or portions thereof, and
its various modifications (hereinafter "the functions") can be
implemented, at least in part, via a computer program product,
e.g., a computer program tangibly embodied in an information
carrier, such as one or more non-transitory machine-readable media
or storage device, for execution by, or to control the operation
of, one or more data processing apparatus, e.g., a programmable
processor, a computer, multiple computers, and/or programmable
logic components.
[0036] A computer program can be written in any form of programming
language, including compiled or interpreted languages, and it can
be deployed in any form, including as a stand-alone program or as a
module, component, subroutine, or other unit suitable for use in a
computing environment. A computer program can be deployed to be
executed on one computer or on multiple computers at one site or
distributed across multiple sites and interconnected by a
network.
[0037] Actions associated with implementing all or part of the
functions can be performed by one or more programmable processors
executing one or more computer programs to perform the functions of
the calibration process. All or part of the functions can be
implemented as, special purpose logic circuitry, e.g., an FPGA
and/or an ASIC (application-specific integrated circuit). In some
implementations, at least a portion of the functions may also be
executed on a floating point or fixed point digital signal
processor (DSP) such as the Super Harvard Architecture Single-Chip
Computer (SHARC) developed by Analog Devices Inc.
[0038] Processors suitable for the execution of a computer program
include, by way of example, both general and special purpose
microprocessors, and any one or more processors of any kind of
digital computer. Generally, a processor will receive instructions
and data from a read-only memory or a random access memory or both.
Components of a computer include a processor for executing
instructions and one or more memory devices for storing
instructions and data.
[0039] Elements of different implementations described herein may
be combined to form other embodiments not specifically set forth
above. Elements may be left out of the structures described herein
without adversely affecting their operation. Furthermore, various
separate elements may be combined into one or more individual
elements to perform the functions described herein.
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